X-Message-Number: 0019.5 Subject: The Technical Feasibility of Cryonics; part #5 Newsgroups: sci.cryonics From: (Ralph Merkle) Subject: The Technical Feasibility of Cryonics; part #5 Date: 22 Nov 92 21:18:04 GMT The Technical Feasibility of Cryonics PART 5 of 5. by Ralph C. Merkle Xerox PARC 3333 Coyote Hill Road Palo Alto, CA 94304 A shorter version of this article appeared in: Medical Hypotheses (1992) 39, pages 6-16. ---------------------------------------------------------- REFERENCES 1. "Engines of Creation" by K. Eric Drexler, Anchor Press, 1986. 2. "Nanotechnology: wherein molecular computers control tiny circulatory submarines", by A. K. Dewdney, Scientific American, January 1988, pages 100 to 103. 3. "Foresight Update", a publication of the Foresight Institute, Box 61058, Palo Alto, CA 94306. 4. 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The reason is that direct ionizations from background radiation are the only source of damage at such temperatures. Ordinary chemical reactions cannot occur. The pertinent question then is not storage stability, it is how can one get cells down to -196 degrees C and back without killing them."[42] The record for storage is held by Leonard Hayflick, who has kept normal fibroblasts from embryonic human lungs in liquid nitrogen for 28 years (as of June 1990) without noticeable deterioration[96]. 2) There is no implication here that the most powerful repair method either will (or will not) be used or be necessary. The fact that we can kill a gnat with a double-barrelled shotgun does not imply that a fly-swatter won't work just as well. If we aren't certain whether we face a gnat or a tiger, we'd rather be holding the shotgun than the fly- swatter. The shotgun will work in either case, but the fly-swatter can't deal with the tiger. In a similar vein, we will consider the most powerful methods that should be feasible rather than the minimal methods that might be sufficient. While this approach can reasonably be criticized on the grounds that simpler methods are likely to work, it avoids the complexities and problems that must be dealt with in trying to determine exactly what those simpler methods might be in any particular case and provides additional margin for error. 3) An atomic mass unit is the same as a Dalton. Different authors in different fields have different preferences for the name used to describe this unit, and so no single abbreviation will satisfy everyone. The use in this paper of the atomic mass unit, abbreviated as amu, was a compromise intended to be most easily understood by the widest audience. 4) A wide variety of mechanical computer designs are feasible. Perhaps the most famous proposal for a mechanical computer was made by Charles Babbage[98] in the early to mid 1800's. Mechanical systems can be scaled down to the molecular size range and still function, although the analysis of such molecular mechanical systems requires the use of (appropriately enough) molecular mechanics: a thriving field which models molecular behavior by the use of force fields to describe the forces acting on the individual nuclei[99]. The time evolution of the locations of the nuclei can be followed using relatively straightforward computational methods. 5) To fully specify the state of each atom would, strictly speaking, require that we specify the states of all its electrons. For the most part, however, these states are known or can be readily inferred once the type of atom is given. For example, a sodium atom in solution will normally be the ion, Na+. Likewise, the bonding structure of two carbon atoms separated by a certain distance can normally be inferred from the distance. The state of magnetization, while relevant for computers (the state of magnetization of a floppy disk is obviously of importance) is of negligible importance in biological systems. People are routinely exposed to magnetic fields of several Tesla to make diagnostic images, and appear none the worse for the experience. While coordinate information should be sufficient in almost all cases, we can always add a few bits of additional information if there is some ambiguity. This won't increase our estimate of 100 bits per atom by very much, and because 100 bits is a conveniently round number we'll continue to use it. 6) Because proteins are always produced as a linear chain, they must of necessity be able to adopt an appropriate three dimensional configuration by themselves. Usually, the correct configuration is unique. If it isn't, it is usually the case that the molecule will spontaneously cycle through appropriate configurations by itself, e.g., an ion channel will open and close at appropriate times regardless of whether it was initially started in the "open" or "closed" configuration. If any remaining cases should prove to be a problem, a few additional bits can be used to describe the specific configuration desired. 7) "For many years, it was thought that irreversible cellular damage unavoidably occurs after only a few minutes of complete cerebral ischemia. This opinion has been modified during the past decade [omitted reference]. Provided that the conditions for recovery are optimal, short-term restoration of brain functions may be achieved after periods of ischemia lasting as long as 60 minutes..."[93]. "Most clinical and experimental studies suggest that the normothermic brain is not able to withstand complete ischemia of >8 to 10 min. There is, however, firm experimental evidence of functional and biochemical recovery of a substantial part of the brain after complete cerebrocirculatory arrest of one hour [omitted references]."[97]. "It turned out in fact that appropriate treatment of post-ischemic recirculation disturbances led to recovery of energy metabolism and neuronal excitability after complete cerebro-circulatory arrest of as long as 1 hour at normal body temperature [omitted reference]"[95]. 8) Definitions that are similar or identical to the one given here are well known in the cryonics literature[23]. 9) This issue is of great concern to computer users. A variety of tools and techniques exist for recovering information from damaged or otherwise inoperative disk drives, with the intent of recovering the memory and "personality" of the computer so that the user will not suffer a (sometimes traumatic) loss. 10) Cryonics will also fail if a person is prematurely thawed. This failure mode, however, is not an argument against cryonics, rather it is an argument for reliable refrigerators. A person injured in a car crash might die if their ambulance was struck by a train. This is not an argument that we should cremate accident victims rather than use an ambulance to transport them to a hospital! 11) There is fairly general agreement that death by the information theoretic criterion wil not occur during storage of tissue at the temperature of liquid nitrogen, confer footnote 1. For this reason we neglect the possibility that significant information loss occurs during storage even though this might be viewed as theoretically possible. 12) Criticisms of cryonics are not supported by the extant literature. Interestingly (and somewhat to the author's surprise) there are no published technical articles on cryonics that claim it won't work. As one might suspect, there are also no articles in the neuroscience literature that address the issue of erasure of memory in the information theoretic sense, and there are no articles in the cryobiological literature that address the impact of freezing on the retention of long term memory in the information theoretic sense. There is an almost absolute conceptual failure to either understand or consider the implications of the information theoretic criterion of death. This conceptual failure is a severe impediment to research in this area. Even worse, the Society for Cryobiology has gone so far as to adopt by- laws calling for the expulsion of members who support cryonics. Members in good standing who support cryonics have been threatened with firing if they discuss their views publicly. Open discussion and review has proven to be a remarkably effective engine for driving scientific advance. The suppression of open discussion by a scientific society runs counter to one of the most central principles of scientific research and seriously impedes progress. 13) Many non-mammalian animals can be frozen to temperatures as low as -50 degrees C and survive[57]. 14) A majority of the population favor "death with dignity" laws which, once enacted, would give the individual control over the conditions of their own legal death. Once such laws are enacted it should be possible in many cases to eliminate the ischemic interval entirely. 15) There are various reasons for delay when a person is cryonically suspended, ranging from purely pragmatic issues such as delay following abrupt and unexpected accidents to legal and social forces that mandate that suspension not be started until after a legal declaration of "death." Whatever the cause, the effect is to increase the level of damage that takes place prior to suspension. 16) It should be clear that the claim of "irreversibility" is unsupported. Mitochondrial function is well understood: they provide energy for the cell. Even the complete absence of mitochondria would not cause death by the information theoretic criteria. 17) Much current work advances the (correct) claim that cellular, organ, and body function is lost under certain conditions. This loss of function is incorrectly and misleadingly labeled "death," "irreversible injury," etc. This work forms the backdrop against which tissue damage to cryonically suspended patients is measured by most biologists, cryobiologists, doctors and other health care workers. Clearly, this work predisposes such workers to dismiss cryonics because, by these criteria, much "irreversible" damage has occurred in most cryonically suspended patients. The implications of adopting the information theoretic criterion of death have simply not been considered, and we can reasonably expect a delay of several years to a few decades before they are. This would be consistent with historical data concerning the slow acceptance of new ideas. Ignaz Semmelweis demonstrated in 1848 that washing your hands in chlorinated lime after leaving the autopsy room and before entering the maternity ward reduced maternal deaths from childbed fever from as high as 25% to about 1%. Despite this, his proposal was widely ridiculed and little practiced for several more decades[60]. Interestingly, few of even the most severe critics of cryonics claim that death by the information theoretic criterion is likely to have occurred when the question is posed to them directly. 18) It is interesting to note that current research into the three- dimensional structure of neurons often embeds neural tissue in plastic, and then produces a series of thin sections (typically 50 to 100 nanometers thick in electron microscopic reconstruction work) by using an ultramicrotome. The serial sections are then examined by a person (typically a graduate student) and the structures of interest in each section are outlined on a digitizing tablet and entered into a computer. The resulting data-base is used to build a three-dimensional image of the neuron[54]. This work has been quite successful at determining the three-dimensional structure of small volumes (small enough for a graduate student to examine in a few weeks or months) despite the adverse effects of tissue preparation and sectioning. Sections vary in thickness. They also buckle, fold, and tear. Despite these difficulties, the human visual system can reconstruct the original shape of the object in three dimensions. Current electron microscopic reconstructions are quite capable of analyzing even the finest dendrites and thinnest axons, as well as determining the location and size of synapses[27,28], and even finer detail[29]. It seems reasonable that the less damaging method of inducing a fracture at low temperature, and the more informative and less damaging analysis possible with nanotechnology (as opposed to destructive analysis of thin sections by a high energy electron beam) will produce more information about the structure being analyzed. 19) Under favorable circumstances, we might be able to terminate the division process sooner. That is, it might be that a relatively large piece of tissue (several tens of microns or larger) was relatively intact, and required little if any repair. Devising methods to take advantage of the minimal damage that might occur under favorable circumstances is beyond the scope of this paper. 20) For those concerned about the omission of water molecules and the like, we could just as easily store the coordinates of every molecule. This would increase the storage requirement, but would still be entirely feasible. 21) Despite the notorious difficulty in obtaining accurate information about specific aspects of brain "hardware," as discussed by Cherniak[115], it is still the case that rather rough bounds can be usefully derived. 22) A literature search on cryonics along with personal inquiries has not produced a single technical paper on the subject that claims that cryonics is infeasible or even unlikely. On the other hand, technical papers and analyses of cryonics that speak favorably of its eventual success have been published. It is unreasonable, given the extant literature, to conclude that cryonics is unlikely to work. Such unsupported negative claims require further analysis and careful critical evaluation before they can be taken seriously. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=0019.5